1. Field of the Invention
The present invention relates to a stencil printing sheet and a method for stencil-making the same. Specifically, it relates to a stencil printing sheet having a solvent-soluble resin layer and its stencil-making method.
2. Description of the Prior Art
As a stencil printing sheet, a heat-sensitive stencil sheet has conventionally been known which is obtained by superposing a thermoplastic resin film on a porous substrate and adhering to each other. As for methods for preparing heat-sensitive stencil sheet, there have been known the following methods, for example, (1) a method for stencil-making by using a heat-generating device of a flush lamp, infrared lamp or others, superposing a hand-written manuscript or preliminary prepared manuscript on a heat-sensitive sheet, and melting and perforating a thermoplastic resin film by the generated heat from the device described above, (2) a method for stencil-making by using a thermal head for generating a letter image information converted into an electric signal as a dotting heat, bringing a heat-sensitive stencil sheet in contact with the thermal head, and melting and perforating the thermoplastic resin. However, since the methods for stencil-making described above require a series of complicated processes for bringing a light-absorbed and heat-generated manuscript or thermal head in contact with a heat-sensitive stencil sheet, conveying the heat to the thermoplastic resin film in the heat-sensitive stencil sheet to melt the thermoplastic resin film, and subsequently contracting the melted material so as to perforate the thermoplastic resin film, there were some problems, for example, (1) a perforation failure is produced due to the bad contact between a thermoplastic resin film and a manuscript or thermal head for absorbing the heat; (2) adhesion failure is produced due to the nonuniformity in contact pressure of the thermal head, or shrinkage is produced in the heat-sensitive stencil sheet; (3) transfer failure of the heat-sensitive stencil sheet is produced by the melted material of the thermoplastic resin being adhered to the thermal head; (4) printing failure is produced since the melted material is left in the perforated portion and the passage of the ink is prevented; and others.
In recent years, a further improvement in quality of heat-sensitive stencil sheet is demanded. It is demanded to provide such a heat-sensitive stencil sheet that satisfies the smoothness of a thermoplastic resin film, the separating property of the thermoplastic resin film from the manuscript or thermal head, the melting property and the shrinkability of a thermoplastic resin film due to heat, the adhesive strength between a thermoplastic resin film and a porous substrate, and the mechanical strength and abrasion of the porous substrate, and therefore, the condition for producing heat-sensitive stencil sheet becomes complicated and there was the problem that the production cost was accordingly increased.